2021-09-10 07:53:47

by Zhang Yi

Subject: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

Commit 8e33fadf945a ("ext4: remove an unnecessary if statement in
__ext4_get_inode_loc()") forget to recheck buffer's uptodate bit again
under buffer lock, which may overwrite the buffer if someone else have
already brought it uptodate and changed it.

Fixes: 8e33fadf945a ("ext4: remove an unnecessary if statement in __ext4_get_inode_loc()")
Signed-off-by: Zhang Yi <[email protected]>
---
fs/ext4/inode.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d18852d6029c..236adc647eb0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4340,6 +4340,12 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
goto has_buffer;

lock_buffer(bh);
+ if (ext4_buffer_uptodate(bh)) {
+ /* Someone brought it uptodate while we waited */
+ unlock_buffer(bh);
+ goto has_buffer;
+ }
+
/*
* If we have all information of the inode in memory and this
* is the only valid inode in the block, we need not read the
--
2.31.1

2021-09-16 08:05:40

by Jan Kara

Subject: Re: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

On Fri 10-09-21 16:03:16, Zhang Yi wrote:
> Commit 8e33fadf945a ("ext4: remove an unnecessary if statement in
> __ext4_get_inode_loc()") forget to recheck buffer's uptodate bit again
> under buffer lock, which may overwrite the buffer if someone else have
> already brought it uptodate and changed it.
>
> Fixes: 8e33fadf945a ("ext4: remove an unnecessary if statement in __ext4_get_inode_loc()")
> Signed-off-by: Zhang Yi <[email protected]>

Oh, right. Thanks for fixing this. Feel free to add:

Reviewed-by: Jan Kara <[email protected]>

Honza

> ---
> fs/ext4/inode.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d18852d6029c..236adc647eb0 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4340,6 +4340,12 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
> goto has_buffer;
>
> lock_buffer(bh);
> + if (ext4_buffer_uptodate(bh)) {
> + /* Someone brought it uptodate while we waited */
> + unlock_buffer(bh);
> + goto has_buffer;
> + }
> +
> /*
> * If we have all information of the inode in memory and this
> * is the only valid inode in the block, we need not read the
> --
> 2.31.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2021-10-01 04:21:17

by Theodore Ts'o

Subject: Re: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

On Fri, 10 Sep 2021 16:03:16 +0800, Zhang Yi wrote:
> Commit 8e33fadf945a ("ext4: remove an unnecessary if statement in
> __ext4_get_inode_loc()") forget to recheck buffer's uptodate bit again
> under buffer lock, which may overwrite the buffer if someone else have
> already brought it uptodate and changed it.
>
>

Applied, thanks!

[1/1] ext4: recheck buffer uptodate bit under buffer lock
commit: f2c77973507fd116c3657df1dc048864a2b16a1c

Best regards,
--
Theodore Ts'o <[email protected]>